codecov: Bundle Analysis upload persistently 404s on get-pre-signed-url

[qnbs]

Context

@codecov/vite-plugin (wired in PR #605) uploads coverage and Test Analytics successfully via codecov/codecov-action — both confirmed with real ingestion logs ("Upload queued for processing complete"). Bundle Analysis, uploaded separately by the Vite plugin itself, does not.

Evidence

Real CI logs, build job, repeatable across multiple independent runs:

[codecov] Detecting CI provider
[codecov] Detected CI provider: GitHub Actions
[codecov] Attempting to fetch `get-pre-signed-url`, attempt: 1/2/3 — all failed
[codecov] Failed to get pre-signed URL, bad response: "404 - Not Found"

Confirmed reproducing on:

• commit 72b2c777 (before any dashboard-side change)
• commit 1d8fdc43, first run, 2026-09-04 12:21 UTC
• commit 1d8fdc43, diagnostic re-run, 2026-09-04 12:35 UTC — after Bundle Analysis was reportedly activated on the Codecov dashboard for this repo

Ruled out:

• token/auth: the same CODECOV_TOKEN secret works for coverage and Test Analytics in the same runs
• request correctness: verified against the plugin's own compiled source — correct fixed endpoint, correct Authorization: token <uploadToken> header, slug taken directly from GITHUB_REPOSITORY
• propagation delay: the diagnostic re-run happened well after the claimed dashboard activation
• Codecov-wide outage: status.codecov.com showed all systems operational at the time

Current disposition

Non-blocking — codecov.yml's bundle_analysis.status: informational, and the Vite plugin swallows this failure internally (calls Output.write() without emitError), so the build job itself always reports success regardless. This does not gate CI or merges.

Submitted to Codecov via their Bundle Analysis feedback channel. The precise provider/account/backend condition causing the 404 is not established from our side — we can rule out a source-side regression, but do not have Codecov server-side logs.

Not to be confused with

#606, which tracks revalidating @codecov/vite-plugin's declared Vite 8 peer-dependency support — a separate, narrower question. This issue is specifically about the persistent 404, independent of the Vite version question.

Next steps

• Re-check on the next few main builds whether the get-pre-signed-url call starts succeeding
• If Codecov support responds to the feedback submission, record the resolution here
• Close once a build job log shows a successful Bundle Analysis upload